Electrical timing apparatus



Feb. 20, w s n- ELECTRICAL TIMING APPARATUS Filed Feb. 7, 1949 INVENTOR.JAMES W. SMITH ATTORNEY Patented Feb. 20, 1951 ELECTRICAL TIMINGAPPARATUS James W. Smith, Minneapolis, Minn., assignor toMinneapolis-Honeywell Regulator Company, Minneapolis, Minn., acorporation of Delaware Application February 7, 1949, Serial No. 74,938

9 Claims.

The present invention is concerned with an electrical timing apparatus.More particularly, the present invention is concerned with a timingapparatus of the type which is cyclic in operation and is operative tocontrol a relay so that during a first interval the relay will beoberative in a first position and during a second interval the relaywill be operative in a second position.

In certain automatic controls, it is desired to have a pair ofelectrical circuits operated through recycling timing periods ofadjustable length. The present invention accomplishes this recycling tmin by using an electronic circuit whose current flow is regulated bythe charging and discharging of a timing condenser and by a controlledrelay which alternately connects the timing condenser in a dischargingand charging circuit. In order that the apparatus operate consistentlyover a range of adjustment, it is necessary that the linear portion ofthe charging and discharging curve of the timing condenser be utilizedin controlling the conductivity of the controlled electron dischargedevice. This is accomplished in the present invention by operating thecontrol electrode of the discharge device at a voltage that is positivewith respect to its associated cathode.

It is therefore an object of the present invention to provide arecycling timing apparatus which is controlled by a charging anddischarging condenser while operating on the linear portion of thecharging curve of that condenser.

A further object of the present invention is to provide a recyclingtiming apparatus of the type using an electron discharge device whosecurrent flow is controlled by a charging and discharging condenseroperating on the linear portion of the charging curve.

Still another object of the present invention is to provide a recyclingtiming apparatus having an electron dischargev device with a cathode anda control electrode which are connected to a direct current biasingsource tending to cause the control electrode to go positive as anassociated timing condenser is alternately charged and discharged by acontrolled relay.

These and other objects of the present invention will be understood upona consideration of the accompanying specification, claims and drawing ofwhich:

The single figure shows diagrammatically the timing apparatus as it maybe employed for cyclically operating a controlled relay.

Referring to the single figure, the numeral l represents the maincontrol relay of the apparatus and this control relay may be used in anydesired manner to operate to close and open an electrical circuit in arecycling manner as determined by the rest or the control apparatus.

This relay Ill comprises a relay winding II, and switch blades l2 and I3normally biased into engagement, by means not shown, with contacts l4and 16 respectively. Switch blade 13 is normally biased out ofengagement with switch contact l5 when the relay is deenergized. A pilotrelay is indicated by the numeral 20 and this relay comprises the relaywinding 2|, a pair of switch blades 22 and 23 and a pair of switchcontacts 24 and 25. The switch blades 22 and 23 are normally biased, bymeans not shown, out of engagement with their associated contacts 24 and25 respectively. A suitable by-pass or filter condenser is connectedacross the relay winding 2| and functions in the normal manner toby-pass the alternating current flowing in the relay circuit.

Controlling the current flow through the relay winding 20 is an electrondischarge device indicated by the numeral 30. This discharge device maybe one section of a twin triode vacuum tube. The device comprises ananode 3i, a control electrode 32 and a cathode 33.

A further electron discharge device 35 is included in the electricalcircuit for providing a direct current operating voltage. This devicecomprises an anode 36, a control electrode 37 and a cathode 38. Thisdevice may be the other section of the above-mentioned twin triode tubewith its control electrode connected to the cathode. Located in theoutput circuit of this device is a filter network comprising a resistor40 and a condenser 4|. A pair of resistors 42 and 43 form a voltagedividing network across the output of the filter condenser 4|.

A timing condenser 45 is utilized to control the potential differencebetween a cathode 33 and control electrode 32 of the discharge device 30and this timing condenser is alternately connected in a dischargingcircuit and a charg ing circuit by the control relays. Located in thedischarging circuit is an adjustable rheostat 41 while a furtheradjustable rheostat 48 is located in the charging circuit of condenser45.

Supplying power to the apparatus is a suitable power transformer 50which has a primary winding 5| connected to a suitable source of powerand a pair of secondary windings 52 and 53. A main power switch 55 isprovided in the main power lines for initiating operation of theapparatus.

The size of the components of the apparatus may obviously be variedwithout departing from the scope of the invention. The values of oneparticular set of components in the device where it operatedsatisfactorily are as follows: Condenser 4| was 12 mfds., condenser 26was 12 mfds. and condenser 45 was 2 mids. The potentiometers 46 and 41were 2 and 5 megohms respectively. The resistors 40, 42 and 43 were 315,000, 27,000, and 100,000 ohms respectively. The vacuum tube was atwin triode tube known commercially as a IZSN'IGT.

Operation In considering the operation or the apparatus, it will beassumed that the apparatus as shown upon the drawing is in thecompletely deenergized position with the power line switch 55 in theopen position so that no alternating current power is supplied to thecontrol apparatus. When such is the case. the control relays 20 and 10will be in the deenergized position and the associated discharge devicesIll and 35 will be nonconducting. The timing condenser 45 will also becompletely discharged. Upon the closing of the main power line switch55, alternating current will be supplied to the primary winding Ii 01'the power transformer. This will mean that the secondary winding 53 willbe applying an alternating current voltage to the rectifier circuitwhich includes the discharge device 35 and filter network comprising theresistor 40 and condenser 4|.

As soon as current flows in the rectifier circuit there will be avoltage drop across the filter condenser such that the upper terminalwill be positive and its lower terminal will be negative. The circuitfor this current flow may be traced from the upper terminal of secondary53 through conductor 50, resistor 42, resistor 43, conductor 6|,resistor 40, anode 35, control electrode 31 and cathode 33, andconductor 52 back to the lower terminal of secondary 53. With theenergization or secondary winding 52, the electron discharge device 35will also become conductive and the conductive circuit for the dischargedevice 30 may be traced from the upper terminal 01' secondary 52 throughconductor 53, relay winding 21, anode 3|, cathode 33, conductor 54 andconductor 55 back to the lower terminal of secondary 52.

The reason the discharge device 35 will be conductive is that the timingcondenser 45 will not have accumulated a charge and the controlelectrode 32 will be effectively connected to a direct current voltagewhich is positive with respect to the cathode 33. This will be seen whenit is noted that the cathode 33 is connected by way 01' conductors 54and 55 to a tap 51 where the resistors 42 and 43 are joined. The controlelectrode 32 is eflectively connected to the positive terminal 33 on thenetwork connected across the filter condenser 41. This connection may betraced from the control electrode 32 through conductors 53, 10, and 1|,switch contact 14, switch blade i 2, conductor 12, rheostat 41 andconductor 13 to terminal 53.

When the discharge device 30 becomes conductive, the pilot relay 20 willbecome energized and switch blades 22 and23 will move into engagementwith their respective contacts 24 and 25. When contact 23 engagescontact 25, an energizing circuit is completed to the control relay land this circuit may be traced from the input power line 14, throughconductor 15, switch contact 25, switch blade 23, conductor 16, andrelay winding II back to the other input power line 11. When the relayl0 becomes energized the switch blade 12 will be moved out of engagementwith its associate contacts l4 to open the control electrode connectionof discharge device 30 to the tap 53. When the relay 20 becomesenergized, the switch contact 22 engages contact 24 and connects thetiming condenser 45 in a charging circuit to terminals 33 and 15 of theoutput voltage divider connected across the filter condenser 4|. Thischarging circuit may be traced from the terminal 63, which terminal ispositive, through conductor 10, condenser 45. conductors 50 and 10,switch contact 24, switch blade 22, conductor 3|, rheostat 45, andconductor 32 to tap 18 o! the voltage divider. With these last namedconnections completed, the timing condenser 45 will begin to assume anegative potential on its upper terminal and a positive potential on itslower terminal such that the control electrode 32 will tend to gonegative with respect to the cathode 33. Inasmuch as there is a resistorin the form of rheostat 45 in the last traced circuit the charging 0!this timing condenser will be dependent upon the size of the condenserand the amount of resistance in the charging circuit. The latter may beadjusted by means of rheostat 45.

After a predetermined time the control electrode 32 will become biasedsufliciently negative with respect to cathode 33, because of the chargeon the condenser 45, that the current flow through discharge device 30will no longer be capable of maintaining the control relay 20 energized.When the relay becomes deenergized the switch blade 22 will move out ofengagcment with switch contact 24 to open the charging circuit for thetiming condenser 45 and the switch blade 23 will move out of engagementwith its associated contact 25 and open the energizing circuit for relayIt. When this relay becomes deenergized the first timing interval willhave been completed. When the relay 10 becomes deenergized the switchblade l2 will move into engagement with switch contact 14 and theclosure of the electrical circuit resulting in this engagement willconnect the timing condenser 45 in a discharge circuit that may betraced from the lower terminal of condenser 45 through conductor 19,conductor 13, rheostat 41, con-- ductor 12, switch blade 12, switchcontact l4, and conductors 11, 10 and 30 to the upper terminal oicondenser 45.

As the condenser 45 discharges the control electrode 32 will have avoltage thereon which is progressively becoming lass negative withrespect to cathode 33. Since there is a resistor in the form 01'rheostat 41 in the discharging circuit of this condenser the dischargewill take a predetermined amount or time which again will be dependentupon the size of the resistance and the size of the timing condenser 45,and which time can be adjusted by means of rheostat 41. As soon as thecontrol electrode 32 has reached a predetermined potential with respectto the cathode 33, which potential may be equal to or slightly less thanthat of the cathode, the current flow in the discharge device 30 will besuch as to energize the control relay 20 and when this relay becomesenergized the second timing interval will have been completed and thefirst timing interval will have been started over again.

It will be noted that the control electrode 32 is connected to apositive point in the direct current voltage source with respect to thecathode 33. This connection has the effect of overcoming the normaltendency of the control electrode to assume a potential that is slightlynegative with respect to cathode 33, and causes the discharge voltage ofcondenser 45 to be effective over the linear portion or the dischargingcurve. For example, assume that the current flow through device 30necessary to energize relay 20 is had when the control electrode 32 isat the same potential as cathode 33. If the circuit were arranged sothat when condenser 45 was completely discharged, as where both cathode33 and control electrode 32 were connected to terminal 68, the controlelectrode 32 would assume a potential which is slightly negative withrespect to cathode 33 and the relay 20 would not become energized uponthe timing condenser becoming fully discharged. The negative voltage onthe control electrode is the result of several factors inherent in theconstruction of electron discharge devices. Some of these factorsinclude the thermo electric effect of the dissimilar metals used 'in themaking of the control electrode and cathode, and the initial velocitiesat which the electrons are forced from the cathode surface which in turnwill be dependent on the work function of the cathode. Another factor isthe leakage current and the interelectrode capacities of the tube. Thecombination of effects results in an accumulation of electrons on thecontrol electrode and it will tend to hold the current flow in the tubeat a much lower value than would be true if the effects were notpresent.

To overcome this tendency of the control electrode to be negative, it iseffectively connected to tap 68 and cathode 33 is connected to tap 61 sothat the control electrode tends to go to .a potential that is positivewith respect to cathode 33. By selecting a proper voltage drop acrossthe resistor 42, it is possible for the linear discharge portion of thedischarge curve of condenser 45 to be efiective to control conduction ofthe device 30 as well as the operation of the relay 20. This furthermeans that linear adjustment of the rheostat I! will result insubstantially a linear t me adjustment on the operation of the apparatuson the discharging of the condenser 45.

It can thus be seen that the charging and discharging of the condenser45 results in a recycling operation of the pilot relay 20 and the maincontrol relay III with the timing period controlled by the timeconstants of the charging and discharge circuits of the condenser 45. Ifthe relay I is recycled, the blade I3 will move alternately between theccntacts l5 and I6 to open and close a pair of electrical circuits whichmay be used in any desired manner. While a specific embodiment of theinvention has been shown, it is to be understood that it is forillustrative purposes only and the invention is to be limited solely bythe scope of the appended claims.

I claim as my invention:

1. A recycling timing apparatus, comprising in combination, an electrondischarge device having an anode, cathode and control electrode, relaymeans in circuit with said discharge device, a source of direct currentcontrol voltage, a timing condenser having one end connected to saidcontrol electrode and the other end connected to a positive terminal onsaid source, means including said relay m.ans for connecting said oneend to a negative terminal on said source for a first time intervaluntil said condenser is charged independently of any current flow insaid discharge device to a potential which will render said dischargedevice nonconducting and said relay means inoperative, means actuatedupon said relay means becoming inoperative to connect said condenser ina discharge circuit, and means connecting said cathode to anintermediate point on said direct current source so that as saidcondenser discharges said control electrode tends to go to a potentialthat is positive with. respect to said cathode, said discharge devicewhen said control electrode reaches a predetermined potential withrespect to said cathode rendering said relay means operative toterminate a second time interval and restart the first time interval byreconnecting said condenser to said source.

2. A recycling timing apparatus, comprising in combination, an electrondischarge device having an anode, cathode and control electrode, relaymeans in circuit with said discharge device, a source of direct currentcontrol voltage, a timing condenser having one end connected to saidcontrol electrode and the other end connected to a positive t rminal onsaid source, means including said relay means for connecting said oneend to a negative terminal on said source for a first time intervaluntil said condenser is charged independently of any curr-nt flowing insaid discharge device to a potential which will render said dischargedevice nonconducting and said relay means inoperative, a firstadjustable resistor in said last named connection for det rmining thetime duration of said first interval,

means actuated upon said relay means becoming inoperative to connectsaid condenser in a discharge circuit, means connecting said cathode toan intermediate point on said source so that as said cond.nserdischarges said control electrode tends to go to a potential that ispositive with respect to said cathode, and a second adjustable resistorconnected in said discharge circuit to determine the rate of discharge,said discharge device when said control electrode reaches a predetrmined potential with respect to said cathode rendering said relay meansoperative to terminate a second time interval and restart the first timeinterval by connecting said condenser to said source.

3. A recycling timing apparatus, comprising in combination, a condenser,relay means, an electron discharge device having said condenser connectd to the input thereof and said relay means in the output thereof, asource of control voltage, means including said relay means whenenergized by said discharge device connecting said condenser directly tosaid source through a timing resistor to charge said condenser through afirst time interval to rend r said discharge de vice and said relaymeans inoperative, means actuated by said relay means when inoperativeto connect said condenser in a discharging circuit, impedance means insaid dischargecircuit for delaying the discharge of said condenserthrough a s.cond time interval until said discharge device becomesoperative and starts the first interval, and means connecting saiddischarge device to said source so that said device is renderedoperative and inoperative by charging and discharging potentials on saidcondenser which are on the linear portion of the charge and dischargecurves of said condenser.

4. A recycling timing apparatus, comprising in terval until said controlelectrode renders said device inoperative and said relay means becomesdeenergized, means actuated by said relay means when deenergized toconnect said condenser in a discharging circuit, means connected in saiddischarge circuit for dJaying the discharge of said condenser until thevoltage thereon renders said discharge device conductive to restart thefirst interval. and means connecting said cathode to said source so thatwhen said condenser is discharging said control electrode will tend togo to a potential that is positive with respect to said cathode.

5. A recycling timing apparatus, comprising in V combination, a timingcondenser, relay means,

an electron discharge device having an anode, cathode and controlelectrode, means connecting said condenser to said control electrode andsaid relay means in energizing relation to said anode, a source ofdirect current voltage having end terminals and a tap thereon, meansincluding said relay means when energized by said discharge deviceconnecting said condenser to an end terminal of said source to chargesaid condenser through a timing resistor until said control electroderenders said device inoperative and said relay means becomes deenergizedto terminate a first time interval, means actuated by said relay meanswhen deenergized toconnectsaidcondenser in a discharging circuit, meansconnected in said discharge circuit for delaying the discharge 01' saidcondenser until the voltage thereon renders said device conductive toterminate a second time interval and restart the first interval, andmeans connecting said cathode to said tap on said source so that whensaid condenser is discharging said control electrode will tend to go toa potential that is positive with respect to said cathode.

6. A recycling timing apparatus, comprising in combination, an electrondischarge device having an anode, cathode and control electrode, relaymeans in circuit with said discharge device, a source 01' direct currentcontrol voltage comprising a further electron discharge device and afilter network connected in series with an alternating source of power,a timing condenser having one end connected to said control electrodeand the other end connected to a positive terminal on said source, meansincluding said relay means for connecting said one end directly to anegative terminal on said source through a timing resistor for a firsttime interval until said condenser is charged to a potential which willrender' said discharge device nonconducting and said relay meansinoperative, means actuated upon said relay means becoming inoperativeto connect said condenser in a discharge circuit, and means connectingsaid cathode to an intermediate point on said direct current source sothat as said condenser discharges, said control electrode tends to go toa potential that is positive with respect to said cathode, saiddischarge device when said control electrode reaches a predeterminedpotential with respect to said cathode rendering said relay meansoperative to terminate a second time interval and restart the first timeinterval.

7. A recycling timing apparatus, comprising in combination, analternating source of power, an

electron discharge device having an anode, cathode and controlelectrode, relay means, means connecting said cathode to one terminal ofsaid alternating source and said anode to another terminal oi saidsource through said relay means, a source oi direct current controlvoltage having a positive terminal, a negative terminal and a tap at anintermediate point, means connecting said cathode to said tap, a timingcondenser having one end connected to said positive terminal and theother end connected to said control electrode, and means includingswitch contacts actuated by said relay means for alternatinglyconnecting said other end of said condenser to said positive andnegative terminals of said direct current source so that said condenserwill be charged and discharged to control the iiow of current in saiddischarge device in a recycling manner.

8. A recycling timing apparatus, comprising in combination, analternating source of power, an electron discharge device having ananode, cathode and control electrode, relay means, means connecting saidcathode to one terminal of said alternating source and said anode toanother terminal of said source through said relay means, a source ofdirect current control voltage comprising a further electron dischargedevice connected to said alternating source of power and having incircuit therewith a filter network and a tapped output resistor whichhas a positive voltage on one end terminal and a negative voltage on theother end terminal, means connecting said cathode to a tap on saidresistor, a timing condenser having one end connected to said positiveterminal and the other end connected to said control electrode, andmeans including switch contacts actuated by said relay means foralternately con necting said other end of said condenser to saidpositive and negative terminals of said direct current source so thatsaid condenser will be charged and discharged to control the operation01' said relay means in a recycling manner.

9. A recycling timing apparatus, comprising in combination, analternating source 01' power, an electron discharge device having ananode, cathode, and control electrode, first relay means, meansconnecting said cathode to one terminal 01' said alternating source andsaid anode to another terminal of said source through said relay means,a source of direct current control voltage having a positive terminal, anegative terminal and a tap at an intermediate point, means connectingsaid cathode to said tap, a timing condenser having one end connected tosaid positive terminal and the other end connected to said controlelectrode, a second relay means adapted to be energized by meansincluding said first relay means, and means includingswitch contacts 01'said first and second relays i'or alternately connecting said other endof said condenser to said positive and negative terminals of said directcurrent source so that said condenser will be charged and discharged tocontrol the operation of said first and second relay means in arecycling manner.

JAMES W. SMITH.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number

